Air-pump.



J. E. LAFORCE.

AIR PUMP.

APPLICATION FILED JUNE 24, 1912.

Patented Sept. 2, 1913.

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UNITED srarns PATENT OFFICE.

JOSEPH E. LAEORCE, OE NORTH GRAFTON, MASSACHUSETTS, ASSIGNOR TO ALSTEN &

GOULDING- COMPANY, OF WORCESTER, MASSACHUSETTS,

A CORPORATION OF MAS- Specification of Letters Patent.

Application filed June 24, 1912.

Patented Sept. 2, 1913. Serial No. 705,426.

To all whom it may concern.

Be it known that I, JOSEPH E. LAFORCE, a citizen of the United States, residing at North Grafton, in the county of \Vorcester and State of Massachusetts, have invented a new and useful Air-Pump, of which the following is a specification.

This invention relates to an air pump especially capable of use for inflating automobile tires and the like.

The principal objects of the invention are to provide a simple and inexpensive form of double acting pump in which the number of wearing packings is reduced to a minimum, to provide an improved construction of grease container therefor, and to provide improvements in details of construction as will appear hereinafter.

Reference is to be had to the accompanying drawings in which- Figure 1 is a side elevation of a pump constructed in accordance with this invention with the interior casing and some other parts in section to show interior construction and Fi 2 is a central lon itudinal sectional view of a portion thereof.

The invention is shown in the form comprising a base 10 for supporting the stationary part of the pump and having, as usual, a flat bottom on which the operator places his foot to hold the pump in position. Extending upwardly from this base is a pipe 11 constituting a stationary hollow piston rod, screwed into the base and provided at the top thereof with a casing 12 constituting a piston and having inlet ports 13 for the air communicating with the interior of the pipe. On the top of this casing is a flexible cup packing 14 held in position by a nut 15 or the like and at the bottom is a second cup packing 16 held in position by nut 17. These packings 14 and 16 also constitute valves as will appear hereinafter. The free edges of the two cup packings face each other and each is held against a shoulder 18 on the casing by a nut. These nuts have edge notches 19 for the free passage of air. The parts so far described are stationary and they constitute a stationary double-acting piston.

The casing 20 is connected with the handle 21 and is intended to be reciprocated along the piston. This casing is provided at the handle end with a bolt 22 for holding it to the handle and screwed into the upper end of the casing is a plug 23 having a passage 24 connecting with the outer air through the casing by ports 25. This passage preferably extends around the plug inside the casing and is provided with side ports 26 longitudinally arranged and extending to the end of the plug. The end of the plug 23 is provided with a flexible cup packing 27 constituting a check valve with its free edge down and held in position by the bolt 22. The ports 20 open just behind this valve so that air can enter through them behind it and be discharged into the cylinder in the space between the valve and the casing 12. At the opposite end the cylinder is provided with a similar plug 33, passage 34, ports 35 and 36 and check valve or packing 37. They are, however, oppositely arranged so that the free edge of the check valve is up instead of down. In addition to these features at this end the casing is provided with a nut 38 or other fastening device which is adapted to screw on a reduced portion on the plug 33 and hold the check valve. This also fits the stationary piston rod 11. The plug 33 also is provided with a chamber 39 adapted to be filled with grease and having a gland 40 for closingits lower end. This gland is held in position by a nut -1ll having an internal screw thread.

The open lower end of the hollow piston rod 11 opens into a passage H in the base 10 which connnunicates with a fitting -15 having a check valve 1-6 therein which in turn is connected with a flexible tube 17 having any usual form of fitting 48 on the end for connection with the tire nipple.

In operation the handle 21 is reciprocated in the usual way but in this case the reciprocation of the handle carries with it the cylinder so as to move it up and down over the stationary piston. On going up, (as suming that the parts are in the lower position, as shown in Fig. 1) the increase in the space just above the casing 12 tends to reduce the pressure and draw air in through the ports 25 and 2G behind the check valve 27. This creates a difference in pressure between the two sides of the check valve which tends to force the free edges of the check valve away from the walls of the cylinder and permits air to enter under it. In this way the space above the valve 14 is supplied with air on the up stroke. Now on the down stroke, the pressure in the space above the casing 12 Obviously is increased and it forces the check valve 27 firmly against the walls of the casing and prevents escape in that direction. On the other hand, it forces the walls of the check valve 14 away from the casing 20 and permits the air to enter into the space between the two valves 14 and 16. It cannot pass the valve 16, however, as there is greater pressure above it than below it and it is forced out into contact with the walls of the casing. Therefore, it must pass through the ports 13 into the hollow piston rod 11 and down into the passage44. At the same time, as the cylinder goes down, the space below the casing 12 and the valve 16 is increasing and consequently the pressure of the atmosphere outside forces the air in through the parts 35 and 36 and above the check valve 37 in the same way that the air entered below the check valve 27. Thus on the down stroke the air previously entrapped between the cylinder 12 and check valve 27 .is compressed and forced out of the pump through the connection 45, and at the same time air is bein collected in the space below the casing 12. ow on the next up stroke the reverse action takes place, the air below the casing 12 is compressed and forced past the valve 16 into the hollow piston rod 11 through the ports 13, while more air is being taken in above. In this way a practically continuous action is secured and each half stroke is a compression stroke and also draws in a supply of air to be compressed on the next half stroke. Obviously the check valve 46 permits the compressed air to be forced along the tube 47 outwardly, but if the back pressure is excessive, it closes and prevents the loss of air from the tire. It will be seen, therefore, that a very effective and yet inexpensive construction is secured in which the only wearing valves or packings are the cup valves 14 and 16 and the packing at the bottom of the cylinder. Also the cylinder is accurately guided by the long bearing formed at the two ends of the grease cup and the parts are easily dismountable and readily inspected and repaired.

While I have illustrated and described a; preferred embodimentof the invention I am aware that many modifications can be made therein by any person skilled in the art without departing from the scope of the invention as expressed in the claims. There fore, I do not wish to be limited to all the details of construction herein shown and described, but what I do claim is 1. In an air pump, the combination of a stationary piston, a reciprocable cylinder fitting said piston, a hollow block secured to the end of the cylinder and having ports for the admission of air into the cylinder, means at the inner end of the block, whereby air can be admitted into the cylinder from said ports, but cannot be exhausted therefrom, and a stationary hollow piston rod connected with said piston and extending through the block. V

2. In an air pump, the combination of a piston, a cylinder fitting said piston, a hollow plug screw-threaded into the end of the cylinder and having ports for the ad -mission of air into the cylinder, means on the inner end of said plug whereby air can be admitted into the cylinder but cannot be exhausted therefrom, and a piston rod connected with said piston and extending through the plug.

3. In an air pump, the combination of a piston, a cylinder fitting said piston, a hollow plug screw-threaded into the end of the cylinder and having ports for the admission of air into the cylinder, a flexible cup shaped check valve on the inner end of said-plug, whereby air can be admitted past the check valve but cannot be exhausted therefrom,

and va hollow piston rod extending through said plug, said plug being provided with a grease cup surrounding the piston rod.

4. In an air pump, the combination of a piston and piston rod with a cylinder therefor, said cylinder having a hollow plug II1 the end fitting the rod, said plug being provided with means for permitting the'air'to pass by it into the cylinder and having a hollow chamber surrounding the rod for receiving a lubricant, and a nuton the outside of the plug for closing the chamber.

In testimony whereof I have hereunto set my hand, in the presence of two subscribing witnesses.

JOSEPH E. LAFORGE. I

Witnesses I I-IoRATIo C. GOULDING, O. Fonnnsr WESSON.

(iop ies of this patent may be obtained for five cents each, by addressing the Commissioner ofPatents,

Washington, D. C. 

